Radio loud speaker and the like



Aug. 18, 1931. c. H.' DUFFY 1,818,987

RADIO LOUD SPEAKER AND THE LIKE Filed June` 30, 1930 Patented Aug. 18, 1931 PATENT OFFICE CHARLES HUGH DUFFY, OF MIAMI, FLORIDA.

RADIO LOUD SPEAKER AND THE LIKE i Application led June 30, 1930. Serial No. 484,788.

REISSUED (GRANTED 'UNDER THE ACT 0F MARCH `3, 1883, AS AHENDED APRIL 30, 1928; 370 0. G. 757) The invention describedherein lmay be manufactured and used by or for the Government for governmental purposes, without the lpayment to me of any royalty thereon.

T is invention relates to radio loud speakers and the like, but more particularly to a drive system therefor, and has for its object to incorporate improvements over my U. S. Patent No. 1,740,161 dated Dec. 17,

1929, whereiri two or more driving units are employed.

In radio and like loud speakers wherein the diaphragm is driven by a sin le unit, such unit can, by a plurality of fie d windings or by other known means, be caused to be pitched to a high resonance in order to accentuate the reproduction of thel high frequencies vand slight the value of the lows, or it may be pitched to a low resonance to accentuate the reproduction of the low frequencies and slight the value of the highs. Such a system however does not contemplate an accentuation of both the high and low frequencies at the same time, nor does it provide for the variations of 'simultaneous accentuations of both high and low frequencies.

In the present invention, I prefer to employ a plurality of diaphragm driving units, or pulsating current impulse responsive devices, preferably two, each of which has preferably three `field windings. One of the windings being of a relatively low impedance or ohmage resistance in order to let through the high frequency pulsations and relatively restrict the lows. The .other ofk the windings being of a relatively medium impedance or ohmage resistance so as to let through the high and low frequencies with equal facility and thus pitch the reproduction at medium values. The other ofv the windings being of a relatively high impedance or ohmage resistance so as to 're-A strict the highs and let through the lows to pitch the reproduction to a low resonance.

In the example shown in the accompanying drawings, two such diaphragm driving units are illustrated.

By such an arrangement, andby the construction which will be presently described,

the reproduced sound may be pitched to produce six different tonal changes, while by reason of the instrumentality provided for causing the driving units to deliver simultaneous but opposed pulsationsto the vibratory diaphragm, or diaphragms, these six tonal changes may be increased to twelve differentk tonal changes; all of which instrumentalities will be first fully described and Y afterwards specifically pointed out in the ap ended claims.

eferring to the accompanying drawings:

Fig. 1 is a diagrammatic view of one example of the component parts of the s stem.

Fig. 2 is a frontelevation of lthe se ective switch.

Fig. 3 is a rear elevation of the same and Fig. 4 is a cross sectional view through the same.

Like numerals of reference indicate the same parts throughout the several figures, in which: s

,R represents the receiver, and 1 and 2 represent the wires through which the pulsating current isdelivered therefrom.

As shown in the example illustrated in Fi 1, the wire 1 passes to the three fields win ings of the diaphragm drive unit A, and also to one center pole 3 of the reversing switch S. The otherwire 2 passes to a binding post 4 of the selective switch T, and also to the other of the central poles 5 of the reversing switch S.

vConnecting a pole 6 of the reversing switch S with a binding post 7 of the selective switch T, is a wire 8. Three switch binding posts` 9, 10, and 11, Fig. 3y are connected by wires 12, 13 and 14 to the three taps 15, 16, and 17 of the three field windings 18, 19 and 20 of the drive unit B, while three switch binding posts 21, 22 and 23 are connected by wires 24, 25 and 26 to the three taps 27, 28 and 29 of the three field windings 30, 31 and 32 of the drive unit A.

Connecting the pole 33of the reversing switch S with the three field windings 18, 19, and 20 of the drive unit B, is a wire 34. The poles 35 and 36 of the reversing switch S are connected to the poles 6 and 33 thereof by crossed wires as dlagrammatically shown, or the reversal of the direction of How of pulsating current from the receiver R to the drive unit B may be effected by any other known means.

Referring now to the selective switch T, it will be seen from Figs. 2, 3, and 4 of the drawings that the same embodies an insulating base 37, and insulating arm 38 carried on a shaft 39 centrally mounted in the base 37.

Arcuately arranged on the base 37, are two series of switch contacts A' and B'. Each of the contacts of these series have preferably semi-spherical heads standing above the plane of the hase 37, and each series comprises live and dead contacts alternately arranged, the dead contacts being shown black.

In the series A' the first and last or end contacts are live, each alternate contact being dead, while in seriesB, the first and last or end contacts are dead, each alternate contact being live. The result of this arrangement is that a live contact of one series is diametrically opposite to a dead Contact of the other series, and a dead contact of one series is diametrically op'posite to a live Contact of the other series. `lhe four live contacts of series A' are indicated by the characters a', a2, a3 and at, while the three live contacts of series B are indicated by the characters b',- b2 and b2. The dead contacts of both series are indicated by the letter d.

Arranged intermediate the series of contacts A and the central shaft 39 is an arcuate or segmental stationary contact A2, common to the series A', and supported at each end in two posts 4 which form stops for the insulated 'arm 38, one of which posts forms a binling post for the wire 2 from the receiver Intermediate the series of contacts B and central shaft 39 is an arcuate or segmental stationary contact B2 common to the series B and supported at each end in two posts 7, one of which forms a binding post for the wire 8 from the reversing switch S.

The insulated contactcarrying arm 38 eX- tends over the two arcuate or segmental contacts A2 and B2 and carries at each end thereof a spring double contact or brush; One of these A2 is formed, for instance, as shown in Fig. '4, the outer end terminatin in a V shaped contact or brush to engage t e series of contacts A', while the inner end is curved as shown and engages the commonarcuate or segmental contact A2. The other of these spring double contacts B2 is formed, for instance, as shown in Fig. 4, the outer end being Hat and bifurcated (Fig. 2) to engage -the series of contacts B', while the inner end is curved as shown and engages the common arcuate or segmental contact B2.

Having thus described the construction,

the operation of the selective switch is as follows:

Froml Fig. 3 it'will be seen that the two end line contacts of series A' are connected together by a wire C, and from Fig. 2, it will be seen that the V shaped end of the spring contact A3 is in electrical contact with the live end contact and the adjacent dead contact of series A', while it will be understood from Fig. 4, the inner end of the spring contact A8 is always in electrical contact with the Icommon arcuate or segmental contact A2.

It will be seen from Fig. 2 that the flat bifurcated end of the spring contact Bs is wide enou h to make contact with two of the contacts o series B', and when the V shaped end of-contact A3 is in contact with two live and dead contacts of series A', the flat bifurcated end of spring contact B3 is in contact with two live and dead contacts of series B', while the inner curved end of spring contact B8 is always in contact with the common arcuate or segmental contact B2 (Fig. 4).

The switch being in position shown in Fig. 2, the circuit from the receiver R passes to the drive unit A or pulsating current impulse responsive device through the selective switch T. This circuit is through wire 2 from receiver R to binding post 4 of the common arcuate or segmental contact A2 and l through the spring double contact A3 to the switch contact a' and through the wire 24 to the tap 27 of the low impedance field winding 30, which for instance may be of the order of 500 ohms. This winding pitches the drive unit A or impulse responsive device to a high resonance.

The circuit from the receiver R to the drive unit'B passes through the wire 2 to the central pole 5 of the reversing switch S and to the binding post 33 of the reversing switch and through the wire 34 to the low impedance ield winding 18 and through the wire l2 to the switch contact b' of series B'; then through the spring double contact B3 to the common arcuate or segmental contact B2 and its binding post 7 through the wire 8 to thc pole 6 of the reversing switch S. From the center. pole?) of the reversing switch S the circuit leads to the receiver R.

It will thus be seen that when the selective switch T is in position vshown in Fig. 2, the low impedance windings of both drive units A and B are in circuit, which pitches both drive units or impulse responsive devices to a high resonance. It will also be seen that when the central-poles 3 and 5 of the reversing switch S are connected to the poles 6 and 33 as in the circuit justl described, the direction of low of the pulsating current from the receiver R to lthe drive unit B is the reverse of that to the drive unit A. This causes positive impulses of drive unit A to be simultaneously accompanied by iegatve impulses of drive unit B. When the units A and B are connected at different points to a common diaphragm or to two diaphra s and in such a circuit, positive sound pro ucing impulses are imparted by one portion of the single diaphragm, or by one diaphragm simultaneously withnegative sound producing impulses imparted by another portion of the diaphragm or by another adjacent diaphragm from the same side of the diaphragm or diaphragme. The acoustical effect of this diaphragm action is that diaphragm and unnatural resonance is eliminated, the audibility of the low frequencies is impaired and the moderate and high frequencies are sharpened. When the action of one of the drive units is thus reversed, the effect is particularly favorable to the reproduction of the speaking voice, where the elimination of fuzzy resonance is desirable and sharpness and definition of the spoken words essential.

Referring again to Fig. 2, it will be seen that as the arm 38 is moved clockwise, the V shaped end of the spring contact As breaks contact with the live switch contact a and rides up over the adjacent dead contact d. At the same ktime the'bifurcated flat end of the spring contact B3 leaves the end-most dead contact d of the series B and wipes over theadjacent live contact b. During these movements, the circuit to the drive unit A is broken, but the circuiteto the drive unit B is maintained. The movement is therefore accompanied by no break nor interruption in the reproduction, as the entire output from the receiver R is passing to the drive unit B during this brief period. The clockwise movement being continued, the said V shaped end of the spring contact As drops down between the dead contact d, over which it has ridden, and the next adjacent live contact a2 and establishes electrical contact with the live contact a2'. At the same time, the bifurn cated flat end of the spring contact B3 asses over the live contact b and on to the adgacen't dead contact d without breaking contact with said live contact b.' The drive unit B is thus maintained in its circuit, but a new cir cuit has been established for the drive unit At The switch Contact a2 of series A is connect-- ed to the highest impedance field winding 32 of the drive unit A, by the wire 26 and this field winding is thus brought into the circuitC This pitches the drive unit A to its lowest resonance, while the drive unit B is stili pitched to its highest resonance. The accusm tical eii'ect of this combination is that the fullest ran e of which the system is capable is obtaine The high frequencies are re produced at their maximum by the drive unit B, while the low frequencies are reproA duced at their fullest values by the drive unit A. An audible click is produced at the instant the V shaped end of the spring contact Ali drops down into contact with the 'iive switch contact a2 and the tension cf. the

spring contact A is sufficient to maintain both contacts A2 and B2 against casuaf movement in either direction.

When it is desired to change to any of the other combinations to modify the resonance of the reproduction, as for instance to pitch the same to the lowest resonance of which the system' is capable, the 'arm 38 is again moved clockwise. This causes the V shaped end ofthe spring contact A3 to ride up on the live switch contact a2 and maintain its contact therewith. At the same time the bifurcated dat end of sprin .contact B8 breaks contact with the live switc contact b and passes over the adjacent dead contact d. These movements result in maintaining the drive unit A in circuit and breaking the circuit of the drive unit B, so that durin this brief interval, the reproduction is unroken and uninterrupted.. `Continued movement of the arm 38 clockwise causes the V shaped end of the spring Contact A3 to drop down between the live switch contact a2, with which it is in contact, and the adjacent dead Contact d, thus maintaining contact with said live switch contact a2 and maintaining the highest impedance eld winding 32 of the drive unit A in circuit. At the same time the bifurcated fiat end of spring contact B8 passes into electrical contact with the adjacent live switch contact b2 and connects the highest im edance field winding 2G of the drive unit in the circuit through. the Wire 13. lThis changes the pitch of the resonance of the drive unit B from the highest to the lowest and as the corresponding highest impedance field winding 32 of the drive unit A is maintained in, circuit as just de ribed,

,both drive units A and B are pitched te their iowest resonance.

Further selective movement of the. maintains the drive unit B in circuit tinue the reproduction without brca terruption and after momentaril b ing the circuit of drive unit A, establ i I lianes another circuit by'brin ing the inte e field winding 31 of drive unit A circuit throughthe switch contact as and the wire 25. This movement maintains pitch of the drive unlt B at its lowest resonance and changes the pitch of the drive unit to a field winding 19is bron ht in circuit, This pitches both drive units resonance.

Further movement of the arm 38 maintains the drive unit B in circuit to continue the reproduction without break or interi" but estabiishes another circuit for c i Je unit A in which the lowv impedance field winding' lof the drive unit A in brought incircuit. This pitches the drive unit A to a high iesoand B to a medium nance and maintains the drive unit B at a medium. resonance.

It will be seen from Fig. 3 illustrating a rear view of the selective switch shown in Fig. 2 that the two endmost live'contacts `of series A, which as will appear from Fig.

2 are contacts a and a4, are electrically connected together. Consequently when the movable Contact As is in contact with either of these two endmost live contacts a and a, the same circuit to the drive unit Aris closed through the wires 2 and 24, as will be apparent from Fig. 3. For instance from Fig. 2, it will be seen that while contacts B2 and b are connected as shown, contact A2 and a arevconnected, but as contacts a and a* are electrically connected Fig. 3), the circuit is the same as if the A.mova le contact Ai were in physical contact with the contact A".

It will be noted that in the operation of the selective switch T, to change from one point to another the circuits of the drive units A and B are alternately broken, and' that at no time is there any break in the reproduction, because while the switchis changing one of the drive units from one pitch resonance to another, the circuit of the other of the drive units is maintained unbroken. y

In the example shown in which the drive units are each provided with three field windings of different impedances, six combinations are Bbtainable to eiect six different tonal changes in the reproduction by the selective switch T. As each of these combinations can be again changed by the reversing switch S, a total of twelve diferent tonal change is available in the example shown.

While I have disclosed one example of the system, the pitch of the resonance of the two drive units or impulse responsive devices may be changed in any known manner other than by different or tapped field windings, as for instance by fixed or variable condensers', and the units or impulse res onsive devices selectively brought into various combinations as y a selective switch such for instance as herein described.

Having thus described one example of the invention, what I claim as new and desire to secure by Letters Patent of the United States is':

1. A drive system for radio loud speaker diaphragms and the like including two diaphragm actuating units, each of which includes a plurality of field windings of difierent impedances, a source of pulsating electric current, -an electrical circuit, a selective switch including two series of switch contacts, one series of said contacts for each actuating unit and for electrical connection with the plurality of field windings of each actuating unit, and a reversing switch in electrical circuit with one of the actuating units and disposed electrically between the source of pulsating current and the selective switch, whereby the direction of flow of pulsating current through the field windings of one un1t may be reversed with respect to the direction of flow of the pulsating current through the iield windings of the other of the actuating units.

2. A drive system for radio loud speaker diaphragms and the like, including two diaphragm actuating units each of which includes a plurality of field windings of diierent impedances, a source of pulsating electric current, an electrical circuit, a selective switch including two series of switch contacts for electrical connection with the pluralit of field windings of the actuating units, w ereby any one of the field windings of one actuating unit may be connected in circuit with any one of the field windings of the other actuatin unit, and a reversing switch in electrica? circuit with one'of the actuating units, whereby the direction of fiow of pulsating current through the field windings of one unit may be reveresed with respect to the direction of fiow of pulsatin current through the field windings ofthe ot er of the actuating units.

3. A drive system for radio loud speaker diaphragms and the like, including two diaphragm actuating units, each of which includes a plurality of field windings of derent impedances, a source of pulsating electric current, an electric circuit, a selective switch includin two series of switch contacts for electrica connection with the plurality of field windings of the actuating units, whereby any one of the field windings of one actuating unit ma be connected in circuit withvany one of the eld windings of the other actuating unit.

4. A drive system for radio loud speaker diaphragme and the like, including two diaphragm actuating units, each of which includes a plurality of eld windings of dinerent impedances, an electrical circuit, a selective switch including two series of switch contacts for electrical connection with the plurality of field windings of the actuating units, whereby any one of the field windings of one actuating unit may be connected in circuit with any one of the field windings of the other actuating unit.

5. A drive system for radio loud speakers and the like including two diaphragm actuating units, and including means for 1m arting to each of the two units a plurality o different pitch resonances, an electrical circuit and a selective switch includin means for electrically connecting in the circuit any one of the plurality of different pitch resonance imparting means for one unit and any one of the plurality of diierent itch resonance imparting means for the oter unit, whereby the sound reproduced by each of the two units may have the same pitch resonance, or the sound reproduced by one unit may have a hlgh pitch resonance and the sound jointly reproduced by the other unit may have a low pitch resonance.

6. A drive system .for radio loud speakers and the like, including two diaphragm actu ating units, an electrical circuit, means for imparting to each of the two units a plurality of `dierent pitch resonances, and a selective parting to each of the two-units a plurality of different pitch resonances, and means for selectively connecting the two units in the circuit to impart to each of them the same or different pitch resonances.

8. A drive system for radio loud speakers and the-like, including two pulsating current impulse responsive devices, an electrical circuit, means for imparting to each of the two impulse responsive devices a plurality of different pitch resonances, and means for selectively connecting the two impulse responsive devices to impart to each of them the same or different pitch resonance.

9. A drive system for radio loud speaker diaphragms and thelike, including two diaphragm actuating units, each of which includes a plurality of field windings, of different impedances, an electrical circuit, a selective switch including two series of switch contacts, one series of said contacts for each actuating unit and for electrical connection with the plurality of field windings of each actuat- 4 ing unit, switch contacts movable over both series of switch contacts to selectively engage a contact .of each series of switch contacts to bring any one of the field windings of one unit, and any one of the field windings of the other unit in the electrical circuit, and a reversing switch in electrical circuit with one of the actuating units, whereby the direction of fiow of the current through the selected field winding of one unit may be reversed with respect to the direction of flow of the current through the selected field winding of the other of the actuating units.

.y 10. A device system for radio loud speaker diaphragms and the like, including two diaphragm actuating units, each of which includes a plurality of field windings of different impedances, an electrical circuit, and a selective switch including two series of switch contacts, one series for each actuating unit and `for electrical connection with the plurality of ield windings of each actuating unit, switch contacts movable over both se ries of switch contacts to selectively engage a contact of each series of switch contacts to bring any one of the iield windings of one unit and any one of the field windings of the other unit inthe electrical circuit.

11. A drive system for' radio loud speaker diaphragms and the like, including two diaphragm actuating units, each of which 1ncludes a plurality of field. windings of different impedances, an electrical circuit, and a selective switch including two'seres of switch. contacts, one series for each actuating unit, the contacts of each seriesbeing op osite to one another, a switch contact mova le over both series of switch contacts to selectively engage opposite switch contacts ,of each series to bring any one of the field windings of both units inthe electrical circuit, and a reversing switch in circuit `with one of the units to reverse the direction of fiow of current to one unit with respect to the' other unit.

12. A drive system for radio loud speaker diaphragms and the like including two diaphragm actuating units, each of which includes a plurality of field windings of different impedances, an electrical circuit, and a selective switch including two series of switch contacts, one series for each actuating unit, the contacts of eachseries being opposite to one another, switch-contacts movable over Yboth series of switch contacts to selectively engage opposite switch contacts of each series to bring any one of the field windings of both units in the electrical circuit.

13. A drive system for radio loud speaker diaphragms and the like, including two diaphragm actuating units and means for imparting to each of the units a plurality of different pitch resonances, an electrical circuit, a. selective switch including two series of switch contacts, the contacts of each series being opposite to one another, a switch contact movable over both series o switch contacts to selectively engage opposite switch contacts of each series to connect one of the plurality of different pitch resonance imparting means of one unit and one of the plurality of different pitch resonance imparting means of the other unit in the circuit and means for reversing the direction of iiow of current to one unit with respect to the direction of flow of current to the other unit.

14. A drive system for radio loud speaker .diaphragme and the like, including two diaphragm actuating units and means for imparting to each of the units plurality of different pitch resonances electrical circuit, a selective switch including two series ci switch contacts, the tacts of each series being opposite ci her, and switch contacts movable over bc i series ci contacts to selectively engage opposite switch contacts of each series to connect one of the plurality of different pitch resonance imparting means of one unit and one of the piurality of difl ferent pitch resonance imparting means of y cludin the other unit in the circuit.

15. A drive s stem for radio loud speaker diaphragms andl the like, including two diaphragm actuating units, an electrical circuit, the units including a plurality of field windin s of different impedances, a selective switch including a series of switch contacts for each unit, each series of contacts ina live contact for electrical connection with each of the plurality of field windings, and also including in alternate arrangement with the live contacts a plurality of dead contacts, the live contacts of one series bein diametrically opposite the dead contacts o? the other series, an arm having contacts movable over each series of contacts, the movable contacts being of a width to engage a live and a dead contact of each series to selectively connect any field windin of one unit and any field wlnding of the ot er unit in the circuit, the herein recited arrangement of switch contacts insuring the holding of a field winding of one unit in the circuit when the connection is broken to a field winding of the other unit as the movable contacts are selectively moved, to the end that the diierent field windings of the two units may be selectively connected and disconnected in the circuit without interruption or break in the sound reproduction, and means for reversing the direction of iiow of the current to one of the units with respect to the direction of flow of the current to the other of the units.

16. A drive system'for radio loud speaker diaphragms and the like, including two diaphragm actuatin units, an electrical circuit, the units inclu ing a plurality of field windings of different impedan'ces, av selective switch including a series of switch con-` tacts for each ,'unit, each" series of contacts including a live contact for electrical connection with each of different field windings and also including in alternate arrangement with the live contacts a plurality of dead contacts, the live contacts of one series being diametrically opposite the dead contacts of the other Aseries an arm having contacts movable over eac series of contacts, the movable contacts being of a width to engage a live and a dead contact of each series to selectively connect an field winding of one unit and any field win 'ng of the other unit in the circuit, the herein recited arrangement of switch contacts insuring the holding of a field winding of one unit in the circuit when connection is broken toa fieldwinding of the other unit, as the movable contacts are `selectively moved, to the end that the di'erent field windings of the two units may be selectively connected and disconnected in the circuit without interruption or break in the sound reproduction.

17. A drive system for radio loudspeaker diaphragms and the like, including two diaphragm actuating units, an electrical circuit,

each unit including a plurality of field windings of different impedances, a selective switch including a serles of switch contacts for each unit, each series of contacts including an upstanding live contact for electrical connection with each of the diiierent field windings, and also including in alternate arrangement with the live contacts, a plurality of upstanding dead contacts, an arm having contacts movable over each series of contacts, the movable contacts being of a width to engage a live and a dead contact of each series to selectively connect an field Winding of one unit and any field wmding of the other unit in the circuit, one of the movable contacts beingV shaped to drop in between a live and a dead contact of one series to prevent casual movement of the movable contacts.

18. A drive system for radio loud speaker diaphragms and the like including two diaphragm actuating units, an electrical circuit, each unit including a plurality of field windings of different impedances, a selective switch in electrical connection with the different field windings of both units, the selective switch including means for selectively connecting any field winding of one unit and any field winding of the other unit in the circuit without simultaneously breaking the circuit through the field windings of both units, and means for reversing the direction of flow of current to one unit with respect to the direction of flow of current to the other unit.

19. A drive system for radio loud speaker diaphragms and the like including two diaphragm actuating units, an electrical circuit, each unit including a plurality of field windings of diilerentimpedances, a selective switch in electrical connection with the different field windings of both units, the selective switch including means for selectively connecting any field winding ofone unit and any field winding of the other unit in the circuit without simultaneousl breaking the circuit through the field Awindin of both units.

20. A drive system for ra 1o loud speaker diaphragms and the like, including two diaphragm actuating units, an electrical circuit, the system including means for imparting to each of the units a plurality of different pitch resonances, a selective swltch for electrical connection with the means for imparting to each unit a plurality of different pitch resonances, the' selective switch including means for selectively connectin in the circuit any one of the plurality of ierent pitch resonance imparting means for one of the units and any one of the plurality of 'different pitch resonance imparting means for the other of the units without simultaneously breaking the circuit through the resonance pitching means of both units, and means for cuit, t

asians? reversing the direction of low of current through the resonance pitching means of one of the units.

21. A drive system for radio loud speakers diaphragme and the like, including two diaphram actuating units, an electrical cire system including means for imparting to each of the units a plurality of different pitch resonances, a selective switch for electrical connection with the means for imparting to eachof the units a plurality of different pitch resonances, the selective switch including means for selectively connectin in the circuit any one of the plurality of di erent pitch resonance imparting means for one of the units and any one of the plurality of different pitch resonance imparting means for the other of the units without simultaneously breaking the circuit through the lresonance pitching means of both units.

22. A drive system for radio loud speaker diaphragme and the like, including two diaphragm actuating units, an electrical circuit, the system including means for im arting to each of the units a plurality of different pitch resonances, means for electrical connection with the means for imparting to each ofthe units a plurality of diiierent pitch resonances and including means for selectively connecting in the circuit any one of the plurality of dilferent pitch resonance imparting means for one of the units and any one of the plurality of different pitch resonance imparting means for the other ofthe units and for maintaining one of the plurality of dii'erent pitch resonance imparting means for one of the units in the circuit, while the circuit is broken through a pitch resonance imparting means for the other unit.

23. A drive system for radio loud speakers and the like including a plurality of pulsating current impulse responsive devices, an electrical circuit, the/system including means for imparting to any of the impulse responsive devices a plurality of different pitch resonances and including means for selectively connectin in the circuit any one of the plurality of di erent pitch resonance imparting means for a part of the impulse responsive devices and any one of the pluralityy of different pitch resonance imparting means for another art of the impulse res onsive devices and or maintaining one of t e plurality of different pitch resonance imparting means for one of the impulse responsive devices in the circuit While the circuit is broken through the pitch. resonance imparting means of part of the lurality of impulse responsive devices, and) means for reversing the direction of ow of current to a part of the impulse responsive devices.

24. A drive system for radio loud speakers l and the like, including a plurality of pulsating current impulse responsive devices, an electrical circuit, the system including means for imparting to any of the impulse responsive devices a plurality of different pitch resonances and including means for selectively connecting in the circuit one of the plurality of different pitch resonance imparting means for a part of the impulse responsive devices and one of the plurality of different pitch resonance imparting means for another part of the impulse response devices and for maintaining one of the plurality of different pitch resonance imparting means for one of the impulse responsive devices in the circuit While the circuit is broken through the itch resonance imparting means of part of t 1e' impulse responsive devices.

25. A drive system for radio loud speakers and the like, including a plurality of pulsating current impulse responsive devices, an electrical circuit, the system including means kfor imparting to one of the lurality of imulse responsive devices a p urality of diferent pitch resonances and means for connecting in the circuit any one of the plurality of different pitch resonance imparting means of one of the impulse responsive devices with another of the impulse responsive devices.

26. A drivesystem for radio loud speakers or the like, including'. a plurality of pulsating current impulse responsive devices, an electrical circuit, the system including ineans for imparting to one of the plurality of impulse responsive devices a plurality of different itch resonances, means for connecting'in t e circuit any ofthe plurality of different pitch resonance imparting means'of one of the impulse responsive devices with another of the impulse responsive devices, and means in the circuit for reversing the direction of flow of pulsating current to a part of the impulse responsive devices.

In testimony whereof I affix mysignature.

. CHARLES HUGH DUFFY. 

